The rate of entry of α-chlorohydrin into rat rete testis fluid has been studied using the 14C- and 36Cl-labelled compound. The α-chlorohydrin crossed the blood-testis barrier and the concentration of radioactivity in rete testis fluid attained blood levels within 45 min. Within 3 hr of a single injection of [14C]α-chlorohydrin, radioactivity was widely distributed in body fluids, and was present in the lipids of the brain, testis, epididymis and epididymal fat pads. No radioactivity was found in tissue lipids following the administration of [36Cl]α-chlorohydrin, which suggests that dechlorination of this compound occurs before its incorporation. Neither a single high dose nor repeated low doses of α-chlorohydrin induced changes in the incorporation of [14C]glycerol into lipids of the brain, testis, epididymis and epididymal fat pad.